EVN promotes the transmission grid to release solar power capacity

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To free up all the new power source projects, it will need to continue to invest in building new transmission grid projects. Photo: Nguyen Thanh

The EVN has recently sent a report to the Department of Electricity and Renewable Energy (Ministry of Industry and Trade) related to press information on the issue of solar power development.

According to the EVN, by the end of June 2019, there were 89 solar power plants mixing power grid with a total capacity of 4,442.3 MW. If including wind power plants, the total capacity of the national renewable energy capacity is 4,880MW, which focuses mainly on Ninh Thuan (1,102MW) and Binh Thuan (995MW).

From June 4-6, there were more than 4,000MW solar power grid operating and concentrating in Ninh Thuan - Binh Thuan. This puts great pressure on the capacity of the transmission grid to discharge capacity. Many times when power plants simultaneously developed, this has caused overloads of related lines and substations.

The EVN stated that renewable energy plants were put into operation in July 2019, with the current grid configuration and when all power sources are generated at the designed capacity, there are many full or overloaded elements.

Specifically, in the case of a 500kV Di Linh MBA more than140 percent overload (opening the ring against overload); 500kV Vinh Tan transformers with 85 percent load; 220kV Thap Cham 2 transformer over 115 percent; 220kV Dai Ninh transformer overload 140 percent.

In addition, the 110kV Thap Cham - Ninh Phuoc - Tuy Phong - Phan Ri transmission line is overloaded up to 260-360 percent (opening the ring to avoid spreading incidents); 220kV Da Nhim-Duc Trong transmission line is overloaded 105 percent; Duc Trong-Di Linh 110 percent overload.

To ensure continuous power supply for additional load and safe operation of the grid, avoid spread incidents occurring on the electrical system, the National Electric System Moderation Center (A0) will have to implement allocation. The power of the plants is suitable for the maximum transmission capacity of the grid.

To minimise the reduction of power projects' capacity, contributing to ensuring additional supply of the system and ensuring safe operation of the grid, in the short term, the EVN said it is directing all units to concentrate all resources to accelerate the construction investment to ensure the progress of transmission, distribution and renovation projects of transmission lines and existing transformer stations. Property will be provided for the clearance of capacity of renewable energy source projects, especially in the province of Ninh Thuan - Binh Thuan.

These include some key projects such as: 110kV Ninh Phuoc - Tuy Phong - Phan Ri circuit 2 transmission line; 220kV Phan Ri substation and connecting 220 kV Ham Tan substation; TBA 220 Cam Ranh.

In addition, EVN also carries out real-time processing of overloading problems through AGC application (automatic equipment system to increase or decrease the capacity of the generator-PV) of SCADA system/ EMS.

In particular, the AGC system automatically calculates and automatically adjusts the power output of plants to ensure no overload of lines and transformers. Therefore, the capacity and output of mobilised factories will be higher than the fixed allocation from the previous day's plan.

Regarding a long-term solution, according to the EVN, since June 2018, it has taken the initiative in researching and proposing the Ministry of Industry and Trade to appraise and submit to the Prime Minister for approval of additional planning for transmission grid projects. The load needed to free up the capacity of wind and solar power sources was approved for additional planning till the end of August 2018 (total solar capacity of 9,500MW and wind power is 2,400MW).

Based on the proposal of EVN and appraised by the Ministry of Industry and Trade, the Prime Minister has approved additional planning of 15 220-500kV power grid projects and looked to on strengthen power grids in Ninh Thuan - Binh Thuan.

Currently, the EVN is directing the National Power Transmission Corporation to urgently invest in putting the above grid projects into operation on schedule.

However, the EVN also stated that from August 2018 to the end of 2018, there were many projects that continued to be approved with additional planning, in which the total capacity scale increased compared to the time when EVN Additional process of transmission grid projects. Specifically, solar power increased from 9,500MW to 12,879 MW (up 3,379MW); Wind power increased from 2,400MW to 4,459MW (up 2,059MW).

Therefore, the EVN said to free up all the new power source projects, it will need to continue to invest in building new transmission grid projects.